/*
 * Copyright 2002-2020 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.codec;

import java.io.ByteArrayInputStream;
import java.util.Map;

import org.reactivestreams.Publisher;
import reactor.core.publisher.Flux;

import org.springframework.core.ResolvableType;
import org.springframework.core.io.ByteArrayResource;
import org.springframework.core.io.InputStreamResource;
import org.springframework.core.io.Resource;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.lang.Nullable;
import org.springframework.util.MimeType;
import org.springframework.util.MimeTypeUtils;

/**
 * Decoder for {@link Resource Resources}.
 *
 * @author Arjen Poutsma
 * @author Rossen Stoyanchev
 * @since 5.0
 */
public class ResourceDecoder extends AbstractDataBufferDecoder<Resource> {

    /**
     * Name of hint with a filename for the resource(e.g. from "Content-Disposition" HTTP header).
     */
    public static String FILENAME_HINT = ResourceDecoder.class.getName() + ".filename";


    public ResourceDecoder() {
        super(MimeTypeUtils.ALL);
    }


    @Override
    public boolean canDecode(ResolvableType elementType, @Nullable MimeType mimeType) {
        return (Resource.class.isAssignableFrom(elementType.toClass()) &&
                super.canDecode(elementType, mimeType));
    }

    @Override
    public Flux<Resource> decode(Publisher<DataBuffer> inputStream, ResolvableType elementType,
                                 @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        return Flux.from(decodeToMono(inputStream, elementType, mimeType, hints));
    }

    @Override
    public Resource decode(DataBuffer dataBuffer, ResolvableType elementType,
                           @Nullable MimeType mimeType, @Nullable Map<String, Object> hints) {

        byte[] bytes = new byte[dataBuffer.readableByteCount()];
        dataBuffer.read(bytes);
        DataBufferUtils.release(dataBuffer);

        if (logger.isDebugEnabled()) {
            logger.debug(Hints.getLogPrefix(hints) + "Read " + bytes.length + " bytes");
        }

        Class<?> clazz = elementType.toClass();
        String filename = hints != null ? (String) hints.get(FILENAME_HINT) : null;
        if (clazz == InputStreamResource.class) {
            return new InputStreamResource(new ByteArrayInputStream(bytes)) {
                @Override
                public String getFilename() {
                    return filename;
                }

                @Override
                public long contentLength() {
                    return bytes.length;
                }
            };
        } else if (Resource.class.isAssignableFrom(clazz)) {
            return new ByteArrayResource(bytes) {
                @Override
                public String getFilename() {
                    return filename;
                }
            };
        } else {
            throw new IllegalStateException("Unsupported resource class: " + clazz);
        }
    }

}
